Control apparatus



Nov. 11, 1952 c. M. SANDERS CONTROL APPARATUS 2 SHEETSSHEET 1 Filed June 3,- 1949 l l -J I I INVENTOR. CHARLES M. SANDERS ATTORNEY Nov. 11, 1952 c. M. SANDERS 2,617,593

CONTROL APPARATUS Filed June 5, 1949 2 SHEETSSHEET 2 INVENTOR. CHARLES M. SANDERS ATTORNEY Patented Nov. 11, 1952 UNITED STATES CONTROL APPARATUS Charles M. Sanders, Glenview, Ill., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application June 3, 1949, Serial No. 97,001

9 Claims. 1

The present invention relates to an improved temperature control apparatus particularly useful for railroad cars.

The copending patent application of Wissmiller et al., Serial No. 698,014, filed September 19, 1945, now Patent No. 2,583,524, granted January 22, 195 2, relates to a temperature control system for railway cars wherein individual heat exchangers along the wall of the car are controlled in a manner to oiiset the effects of changing outside temperature, sun, wind, and the like on the respective walls. The overhead heating system is relied on for the remainder of the heat load and for pickup purposes. This system gives excellent control but tends to be slow in picking up car temperature after standby because the control of the side wall heat exchangers is independent of space temperature. The present control apparatus overcomes this difiiculty by combining the network circuits for the side wall heat exchangers with the overhead control network in such a manner that a deviation in space temperature effects the entire control system but, when the space temperature is satisfied, the side Wall heat exchangers are independently controlled to meet their respective demands.

It is thus an object of this invention to provide an improved temperature control system especially adapted for railway passenger cars.

It is a further object to provide a temperature control system for a space having a plurality of temperature changing devices wherein all of them cooperate to vary the space temperature but wherein certain of the devices thereafter are operated at temperatures determined by outside weather conditions, or a condition indicative of said outside conditions.

It is an additional object to provide a network circuit having a branch with a common output connection and a plurality of parallel branches with separate output connections, with each of the separate output connections being adapted to control separate devices.

It is also an object to provide. a temperature control system particularly adaptable to railway cars and arranged to use all available heating means to restore car temperature upon a deviation in car temperature but wherein important components are normally control-led by condi tionsother than car temperature.

These and other objects will become apparent upon a study of the following specification and drawings wherein:

Figure l is a schematic view of a railway car incorporating the present invention.

Figure 2 is an elevation view, with parts in section, of a side wall heat exchanger as used in Figure 1.

Figure 3 is a sectional view taken on the line 3-3 of Figure 1.

Figure 4 is a schematic wiring diagram on the present apparatus.

Referring to Figure 1, car It includes an overhead heating and cooling apparatus generally designated by the numeral II, and further includes side wall heat exchangers l2 and is extending the length of the occupied space. lieat exchangers l2 and it are disposed along the lower portions of the two side walls and, because they are near the floor, are sometimes referred to as the floor heaters.

As best shown in Figure 2, heat exchanger 22 includes horizontal conduits l5 and i5 connected at their end to form a closed loop. A suitable heat exchange liquid it, such as a mixture of ethylene glycol and water, is circulated through said loop by a conventional motor driven circulator I 1. Any suitable expansion means, such as a closed tank, expansibl'e bellows, or the like, not shown, may be connected to each heat exchanger to accommodate the expansion of the heated liquid. Liquid H6 is heated by a steam pipe l3 extending through lower conduit l5, pipe l8 being connected through a motorized valve id and pipe 25 to the train steam line 2i. The condensate formed in pipe [3 is discharged through a conventional steam trap 22 (Figure 1). To increase the effective radiating area of heat exchanger i2, fins 23 may be secured to conduits l4 and iii in any desired manner. Also, for a purpose which will appear, resistance thermostat is inserted in conduit hi in a manner to respond to the temperature of the circulating liquid 16.

Although only heat exchanger 52 has been described in detail, heat exchanger i3 is identical therewith and includes a circulator 24, a steam pipe 25, a motorized valve 25, a steam trap 2? and a resistance type insertion thermostat 3i. While the components of this heat exchanger are the same as those of i2, they have been given different numbers to reduce confusion in th following description.

Insertion thermostat 39 comprises a temperature responsive resistor 32 wound on a suitable core, provided with the necessary connections, and protected from the liquid [6 by a suitable well. Thermostat 31 is identical to 38 and includes a temperature responsive resistor 33. Of course, any devices which vary an electrical resistance in response to temperature changes or" the sidewall heaters may be used instead of thermostats 38 and 31. Immersion thermostats and 3| cooperate with window thermostats 35 and 36, respectively, in the normal control of their respective heat exchangers. Window thermostat 35-, Figure 3, comprises a temperature responsive resistor 31 and is mounted adjacent the inside of the inner pane of the window glass 38 by an insulated box 39 having an open side toward said glass, said resistor thus responding to the temperature of the inside surface of the inner glass, sun effects, and other factors influencing car wall temperature, such as wind. Obviously, a better response to wind and outdoor temperature is had Where a single pane window is used. Thermostat may be similarly mounted adjacent the inside surface of the outer skin of the car, this arrangement involving less response to sun effects. Window thermostat 36 is similar to 35 and includes a temperature responsive resistor LII! and an enclosing insulated box 4|.

The overhead apparatus II comprises a return air inlet duct 42, a fresh air inlet duct 43 controlled by a damper 44, a blower 55 and a distributing duct 46, said duct 46 having outlet openings lil. A cooling coil 50 is located in duct 46 near the blower and a heating coil 5i is located just downstream from said cooling coil. Cooling coil 50 is supplied with refrigerant, chilled brine or the like, from a source not shown, under the control of a conventional solenoid valve 52. Heating coil 5i is supplied with steam from the train steam line 2I through pipe 54*, under the control of a motorized valve 55. A resistance thermostat 56 is arranged in the fresh air inlet duct 13 and therefore responds to outdoor temperature, and the similar thermostat 5? is arranged in duct 46 downstream from coil 52 and thus responds to the temperature of the air discharged into the car.

Outside air thermostat 56, often called a ductstat, comprises a temperature responsive resistor 58 carried on a suitable core and having the necessary connection facilities. Resistor 58 is preferably formed of nickel wire, or material having similar properties, although, obviously, any material having a suitable temperature coefficient of resistance may be used. Discharge air thermostat 51 includes a temperature responsive resistor 59 and is similar in construction to thermostat 56. Room thermostat GI is another element of the present control apparatus and comprises a mounting means and a temperature responsive resistor 62, plus the necessary connections. As with the other thermostats herein described, temperature responsive resistor e2 may be of any suitable sort, such as nickel wire, but, for the purpose of this disclosure, all of the temperature responsive resistors are considered to have a positive temperature coefiicient of resistance. Obviously, thermostat hi, or a ductstat modification of 6|, may be located in the return air duct 42 rather than in the middle of the car, as shown.

Motor valves I9 and 28 are identical and valve is likewise similar. Motor valve I9, for example, includes angle valve 6t having a reciprocable stem to which is attached a rack 65, rack being operable by pinion 66 driven by motor 67 through a gear train 68. Motor 6i represents any conventional reversible motor and, for the purpose of this disclosure, may be of the sort shown in Figure 2 of Upton Patent 2,423,534, issued July 8, 1947. In addition to adjusting valve 64, rack 65 also adjusts wiper 3:; across resistor I2 of follow up potentiometer In a similar fashion, reversible motor I5 of motorized valve 26 not only adjusts the rack and stem It of angle valve I1, but also adjusts wiper 18 across resistor 79 of follow up potentiometer 8i. Likewise, motor 83 of motorized valve 55 simultaneously operates rack and stem. 8 Of. l e

4 85 and adjusts wiper 86 across resistor 87 of follow up potentiometer 88. For this disclosure, it may be assumed that valves I9, 26 and 55 are closed when their respective racks and stems are in a lowermost position and solenoid valve 52 is closed when deenergized.

Amplifiers 9!, 92, 93 and S5, used to control motors 66, I5 and 85 and solenoid 52, respectively, are preferably all alike and of a discriminator sort wherein one relay or another is energized when a signal is impressed upon it, the relay operated depending upon the phase relation of the input signal. While any amplifier of the sort described may be used, the one described in Figure 2 of the aforementioned Upton patent has been found satisfactory.

Amplifier 9i has input terminals 95 and Si, terminal 96 being grounded, and includes relays 98 and 953, relay 98 being energized when a signal of one phase is imposed on terminal 9? and relay 99 being energized when a signal of opposite phase is imposed on said terminal. Relay 93, when pulled in, causes motor 67 to be energized through common output terminal It! and output terminal I02, motor 6i then running in a valve opening direction. Relay 99, when energized, causes the motor to be energized through terminals Isl and N3, the motor then running in a valve closing direction.

Motor I5 is controlled by amplifier 92 in the same manner as motor 61, amplifier 92 having a grounded input terminal I85 and another input terminal I06, and relays I01 and I68 control the energization of motor I5 through output terminals I89, Iii] and III, relay Ifll operating to drive motor H5 in a valve opening direction and relay I08 operating to close the valve, as above described.

Motor 83 is likewise controlled by amplifier 93 in a manner similar to the control of motor El, amplifier 93 having input terminals H3 and H 3, relays H5 and H6 and output terminals H7, H8 and IE9, motor 33 also being driven in a valve opening direction when a signal of one phase is impressed on terminal I I4 and in a valve closing direction by a signal of opposite phase.

Amplifier 94 has input terminals iii and I22, relays I23 and I24, and operates to energize solenoid valve 52 through output terminals I25 and I27 when a proper signal is impressed on terminal I22.

Amplifiers SI, 92, 93 and 94 are all supplied with current by suitable connections to line wires I23 and I30.

The source of the signals used for controlling the aforementioned amplifiers is an electrical network circuit I32. Network circuit I32 has input terminals or sides I34 and I35, these terminals being energized by secondary winding I 35 of transformer I31. While the terminals o sides I34 and I35 are shown as connecting wires, it seems obvious that effectively the same circuit would result if all the branches were connected to the same terminals, the present arrangement being chosen, however, for clarity and more ease in explaining the functions of the circuit. The lowermost branch of the network comprises a high resistance resistor I38 of potentiometer Illa connected across terminals I34 and I35, wiper Hi0 of the potentiometer being connected through capacitor I AI to ground. This branch is used for balancing the capacity efiects of the network when the system is first put in operation.

The next branch of the circuit comprises, reading from terminal I34 to terminal I35, resistor 62 of room thermostatii, control point adjusting rheostat I42, resistor I43 of calibrating; potentiometer H4 and fixed resistor I45. Wiper I46 of potentiometer I44 is connected to ground. The next parallel branch of the circuit, reading upwardly, and-extending betweenterminals I34 and I35, comprises fixed resistor I41, resistor 81 offollow-up potentiometer 88-, resistor 58 of outside air thermostat 56, resistor 59 of discharge air thermostat 5-1 and fixed resistor I48. Wiper 86 offollow-up potentiometer B8 is an output terminal' for this branch of the network and is connected by wire I49 to input terminal I M of amplifier 93. e I

The'cooling control branch of network I32, extending between terminals I34 and I 35, comprises fixed resistor I5I, resistor I52 of potentiometer I53 and fixed resistor I54,wiper I55 of potentiometer I53 being connected by wire I56 to input terminal I22 of amplifier 94.

The first sidewall branch, just above the cooling bran-ch, extendsbetween terminals- I34 and I35 and comprises'fixed resistor I58, resistor 12 of follow-up potentiometer 13, resistor 32 of insertionthermostat 30, resistor 31 of window thermostat 35 and fi-xed resistor I59. Wiper H of follow-up potentiometer 13 comprises an output terminal for'this branch of thenetwork and is connected by wire- I6I to input terminal 91 of amplifier. The uppermost branch, for the other sidewall heat exchanger, likewise extends between terminals I=34- and I35 andcomprisesa fixed resistor I63, resistor 19 of follow-up potentiometer 8|, resistor 33 of insertionthermostat 3-I, resistor 40 of Window thermostat 36 and fixed resistor I54. Wiper 13 of follow-up potentiometer BI constitutes'the output terminal for this branch of the network and is connected by wire I65 to input terminal I06 of amplifier 92.

Primary winding I61 of transformer I31 is connected to line wires I29 and I30 and thereby energized.

The following resistance values for the above circuits are approximate and are given for illustration only, similar values having been found to work satisfactorily.

Resistor: Ohms resistance I38 50,000 62 500 59 20 I 48; 145 s| 500 I52 I54 500 I53 500 1-2 6 3 2. 63 37 250 I59 187 I63 500 1.3 6 313 -63 4 250 I64 187 1 With double glazedwindows.

Capacitor: Micr'ofarads capacity A separate thermostat I68, set for a relatively lowtemperature such as 60, is provided for standby operation of" valves I3 a11d'26, or. other heat exchange surface, but thisDar-t of the syfs' tem has nothing to do with the present invention and is thereforenotdescribe'd'.

The components of network I32, with the excep-ti'on' ofthe thermostats' and follow-up potentionmeters, and the amplifiers are mounted, for convenience, in a central control panel I69, as shown in. Figure 1.

When the above described system has been installed in a car, each portion of the network circuit is adjusted to give a minimum signal for its respective amplifier and then the capacity balance potentiometer I39 is adjusted to reduce these minimum-signals to their minimum values, thereby compensating for the capacity effects and the like dueto long lead wires to remote components and other such factors that normally tend to give an appreciable residual signal. Once this adjustment has been made, it remains fixed and thus this. portion of the network I32 has no part in the normal operation of the circuit.

To more fully describe the. present apparatus, its function will now be considered.

Operation With car Ii] under standby: control, it may now be placed .in readiness for occupancy by connecting line wires I29 and I30 to a suitable source of alternating current, not shown, the various components of the system then being energized by the circuits previously described. However, before proceeding with this description, let it now be assumed that the analysis of the network circuit will be made at a half cycle instant when the potential of the left side, of terminal I34, of the network is, for instance, positive, and the right side, or terminal I35, is negative. Obviously, at the next half cycle instant, these relations will be reversed but, by considering the balance conditions of the network in terms of potential, at the aforementioned half cycle instant, the phase relations are readily understood Thus, although this description is in terms of potentials, the phase relations of the circuit areireall'y being considered.

It may also be assumed that rheostat I42 is adjusted to require a '70" temperature in the car, with heating being required when the temperature is below this value and with cooling being provided when the temperature is above said value. Further, assume that liquid It in side wall heaters I2-and I3 is controlled to '10 when windowstat 35 or 36 responds to and that each degree below 70 for the respective windowstat requires the liquid in its heat exchanger to increasein temperature 4. Also, thermostats 56 and 51 are assumed to be so related that the air discharged through duct 46 will rise 1 above 70* for every degree drop in outside temperature below 70.

Further, assume that a positive signal impressed on terminals 91, I06, H4 and I22 of amplifiers 51,- 92; 93 and 94 will result in energizing relays 99, I08; H6 and I24, respectively, ofthe'ampl-ifiers, While a negative signal (one of opposite phase)" will energize relays 08, I01, I I5 and I23, respectively.

With the system now in operation, and with the-car temperature low, the outside temperaturelow, the discharge air temperature low, and the liquid temperature of the side wall heat exchangers low, it appears that the car temperature will be increased in the following manner. With the car temperature low, the resistance of resistor I32 is low, therefore terminal I34 of the network is less positive in potential than normal and terminal I35 is more negative than normal, this being due to the comparative low resistance in the branch of the network to the left of Wiper I46, said wiper being grounded. With this condition existing, and emphasized because the resistance of resistor 58 is relatively low due to a low outside temperature and the resistance of resistor 59 of thermostat is relatively low due to the low discharge air temperature, Wiper 86 tends to be negative relative to ground, hence a negative signal is impressed on terminal [M of amplifier 93. As previously related, a negative signal on amplifier 93 causes relay M5 to be energized thereby energizing motor 88 in a direction to open valve 55 and to drive wiper 86 to the right across resistor 81 of follow-up potentiometer 88. This movement tends to diminish the resistance on the positive side of the network and to increase the resistance of the negative side but, because of the low space temperature, the low outside temperature and the low discharge air temperature, it seems likely that the negative signal will persist even though wiper 85 to driven to the right extreme of resistor 8?. Thus, air at the maximum temperature available from the system will be supplied through outlets 41 into car Iil from the overhead system I I.

With terminal IBQ less positive than normal and terminal I35 more negative than normal, wiper I55 of potentiometer I53 tends to be negative, hence a negative signal is impressed on terminal I22 of amplifier 94, thus pulling in relay I 23. However, relay I23 exercises no control on th present system, hence no cooling is provided.

With terminal I3 3 less positive than normal and terminal I35 more negative than normal, and with the resistance of resistor 32 relatively low and the resistance of 31 also relatively lot wiper II tends to be negative, hence a negative signal is impressed on terminal 9! of amplifier 9 I, thereby pulling in relay 98 of said amplifier and causing motor 67 to operate in a valve opening direction. Opening valve I9 causes a greater flow of steam through pipe It to thereby increase the temperature of liquid I6 and additionally, the

opening of valve I 9 causes wiper II to be adjusted upwardly across resistor I2, thereby lowering the resistance on the positive side of the network and increasing the resistance on the negative side of the network. Under the conditions assumed, however, it seems likely that the negative signal will persist even though wiper II is advanced to the top of resistor I2, hence the full available heat is supplied to side wall heat exchanger I2. In a similar fashion, a negative signal tends to be impressed on terminal I06 of amplifier 92, thereby pulling in relay III! and driving motor I5 in a direction to open valve 26 and moving wiper I8 upwardly across resistor I9 in an attempt to rebalance the circuit. Thus, the fully opend valve 26 likewise causes side wall heat exchanger IS to operate at its full capacity. With side wall heat exchanger I2 and I3 operating at full capacity and with the maximum available capacity of the overhead system II being used, the temperature of car II! should rise rapidly.

As the car temperature rises, the resistance of resistor 62 increases and terminal I34 becomes more positive relative to ground and terminal I 35 becomes less negative relative to ground, hence the above described negative signals are diminished. Further, even ahead of car temperature, the temperature of liquid I6 in the side wall heat exchangers I2 and I3 rises and the temperature of the air discharged through conduit 46 increases hence, although the effect of these changes will be discussed individually, it seems obvious that the changes are taking place simultaneously. Although the car temperature rises less rapidly than does the discharge air temperature and the temperature of the liquid IS, the effect on the network is more pronounced as resistor 62 increases in value because of its rela tively greater authority. Asresistor 62 increases in resistance value and terminal I34 becomes more positive and terminal I35 less negative, this tends to diminish the negative signals to the various amplifiers but, normally, the car temperature must rise within a few degrees of its desired temperature before the effects of the higher resistance values of resistors 59, 32 and 33 can be felt. However, as the value of resistor 62 approaches normal, the relatively high resistance of 59, as well as the extreme right position of wiper 86, causes the resistance between wiper t5 and terminal I35 to be relatively high hence wiper 86 now becomes positive relative to ground and a positive signal is thus imposed on terminal II 4 of amplifier 93. When the negative signal impressed on amplifier 93 diminished to a predetermined value, relay I I5 dropped out and now, with a sumcient positive signal on terminal II I to energize relay H6, motor 83 is energized in a direction to drive the valve 55 closed and to move wiper B6 to the left across resistor 87. As wiper 86 moves across resistor BLit adds resistance to the positive side of the network and subtracts resistance from the negative side of the network thereby diminishing the positive signal and, when this signal is diminished below a predetermined value, relay I I6 drops out and motor 83 stops. The partial closing of valve 55 restricts the flow of steam to coil 5| and thereby causes a reduction in the temperature of the air being discharged into the car.

With a full fiow of steam through valve I9, 1iquid It becomes quite hot, therefore resistor 32 has a relatively high resistance value and tends to make wiper II positive, this tendency being increased by the position of wiper II near the top of resistor I2, whereby none of the resistance of resistor I2 is in the positive side of the network and all of the resistance is in the negative side of the network branch. Although the relatively high temperature and resistance of 32 would normally cause a positive signal on wiper II, the signal has remained negative in the description so far due to the relatively low resistance value of 52. However, as the car comes up to tem perature and this resistance value increases, terminal I34 becomes more positive and terminal I35 becomes less negative relative to ground than before. At some point of balance, the negative signal on terminal 91 of amplifier 9! will diminish below the point necessary for holding relay 98 energized hence it will drop out, thus deenergizing motor 61. With a further increase in resistance of 32, or an increase in resistance of I32, the signal on II becomessufiiciently positive to pull in relay 99, thereby energizing motor 61 in a direction to close valve I9 and to move wiper II downwardly across resistor I2 far enough to diminish the positive signal to the point that relay99 drops out andagaindeenergizes motor 61. In a similar fashion, the increase in resistance of resistor 33 causes aclosing operation of valve until the network branch is rebalanced sufficiently to drop out relay .108. As the car temperature approaches .its desired value, as described above, the rate of supply of heat is diminished, thus avoiding overshooting of temperature.

Upon the car temperature reaching its desired value, it then appears that the resistance of 62 is just sufiicientto restore .the potentialof terminals I34 and I35 .to.the.value at which the system is calibrated thus, for the present, resistor 62 may be considered .the .same as a fixed resistor and without influence on the network.

As the car temperature has been rising toward its desired value, motor 83 has been gradually closing oif valve 55 to lowerthetemperature.ofthe air discharged through. conduit .46, in the manner above described, and now, with resistor 62 satisfied, motor 83 willdrive valve 55 to a position wherein sufiicient ,heat will be supplied by coil 5| to maintain the resistance value of 55 sufficiently far above normal (70) .to offset the decrease in resistance of resistor 58 .below normal due to the relatively low outside temperature. Then, should the discharge temperature be relatively high, wiper 86 tends .to .be positive relative to ground, .hence relay H5 is energized and operates motor 83 to.close valve 55 and to advance wiper 86 to the left across resistor 81, to thereby balance the network branch. Exactly the same effect would takeiplac'e iftheresistance value of :58 should increasedue to a rise in outside temperature and, should the .outside temperature fall below its previous value or in the event of a decrease in discharge temperature, the lessened resistanceof 58 or 59,01 both, tends to cause wiper 86 to become negative relative to ground to thereby pullin relay H5 and drive motor 83 in a valve opening direction. As above described, upon resistor 62 reaching its normal value due to a satisfied car temperature, valve 55 is operated to hold a predetermined discharge temperature relative to outside temperature, this temperature value being that calculated to maintain stable conditions in the car.

With resistor 62 at its normal resistance value, there is no signal from the network at wiper I55, and both the relays of amplifier 94 are open, hence there is no cooling provided.

When the car temperature is satisfied and the resistance of 62 normal, valve I9 is adjusted to maintain a predetermined relation between the resistance values of 32 and 31, a relatively low resistance of either 32 or 31, or both, tending to cause wiper H to be negative and therefore causing an opening ofthe valve by pulling in relay 98. Also, an increase in resistanceof either or both of these resistors tending to cause wiper H to become positive relative to ground, causes a closing of valve 19 by energizing .relay 99. Thus, as the temperature of thermostat 35, and therefore the resistance of 37,.is dependent upon outside temperature, wind, solar effects and the like, the resistance of this thermostat is not varied by the present system hence this branch of the network tendsto control valve IS ina manner to adjust the temperature and resistance of thermostat 3D to compensate for the variations from normal of resistor 37. Thus, with the temperature affecting resistor 31 at a value of 50 F., or 20 be1ow normal, the temperatureof thermostat 30 must increase to 1 50 o r above normal, to restore equilibrium conditions.

Likewise, thermostats 3| and 36 control amplifier 92 and motor valve 26 in ,a manner to increase the temperature and resistance ofthermostat 3| as the temperature and resistance of thermostat 36 decreases. While it might seem, at first glance, that valves [9 and 25 could be controlled in parallel from one set of thermostats, attention is directed to the fact that thermostats 35 and 35 not only respond to outside temperature, by responding to the inside temperature of the window or the like, but also respond to the effects of sun and wind. Therefore, if the u h u d shineq t s of h ar Where window thermostat 35 is located, the sun would tend to increase the temperature and resistance of resistor 3-! and thereby require a somewhat lower temperature of the liquid in side wall heater 42 followed by areduction in the temperature and resistanceof resistor :32, as therecom ensa e 1 he embed ed to t t Side of the carby the sun shining on it. The sun h in n the o he s d Q t a ld ha a similar effect on the control of heat exchanger I 3. l-iikewise, on the car, .due to natural wind, rnotion of the car-,or both, and when the outside air temperatpre is lower than car .temp ture tend t .lo erih it pe tu h mostats 35and36byva 'ng amounts depending on its incidence, magnitude, temperature and the like and tends 'to require additional heat em th i wall eeie s Should, for some reason orother, the cartemperature increase beyond the desired value even though it is cold outside, the added resistance pf resistor 52 tends to make terminal I35 more positive than ,normal and terminal 135 less negative {than normal, hence wipers'.86',.l 5-5, 'H and 18 all tend to become positive relative to ground, hence tending to pull in relay H5, 124, 99 and H18. '[his tendsto close valves 55, 19 and 2.6 and ;-toenergize.valve,52, thus not only restricting the heat-supplied to .the car but also bringingon cooling. ids a practical matter, .because the refrigerationcoinpressor isusually controlled by outside temperatureanddoes not start operatinguntilthe outside temperature rises to a predetermined value, such as .60", no actual cooling may be provided "even though valve 52 is opened if the outside temperature should be belowfiO", ior 'instance. Obviously, as the outside temperature-rises to=70 and the car temperature tends to rise above 7'0, valves 55, 19 @5135 ,er el' q v n clo d b t p e m a positive signal on their respective amplifiers. The positive signal onwiper .l 55, and therefore on amplifier 95, .causes energization of relay I 2 and the conseduentopening of va1ve' 52"to pro- .Vide thenecessary cooling.

' As abovedescribed by connecting, the side wall heatlicontrol apparatus into thesalne network used for controlling .the overhea d part :of the system, all of :theI heating capacity of the car is available n reas Pa te nr f t ii 'vhe jd sired v when the ea te peratur .P PPH Q satisfied, the overheadheating apparatus and the two sidetwalllheaters are. independently controlled to meet their.respectiveneeds,g-hence, the present System provides i q .ih i mieeen ee 2931 0f the two side wall-heaters and the overhead appa- .ratu a m m sees-e re ,vvissmill rera p c io i -v ritabl i s m ine a Q ih s a e ie eih ,w eneededsih ny p ovi n a system highly effective in operation' and very ll flexible under adverse conditions. Because many substitutions and equivalents will become apparent upon a study of this disclosure, the scope of this invention should be determined only by the appended claims.

I claim as my invention:

1. A temperature control system for a space enclosed by a plurality of outside walls wherein forced air heating apparatus and a plurality of heat radiating means are used for heating said space, said forced air heating apparatus having an outside air inlet and discharging into said space, space temperature responsive impedance means, separate electrical impedance means responsive to the temperature of each of said radiating means, electrical impedance means individually responsive to the temperature of each of a plurality of outside walls, impedance means responsive to outside air temperature, impedance means responsive to the temperature of the air discharged into said space, a voltage dividing network circuit having input connections and a plurality of parallel branches, the first of said branches including said space temperature responsive means and a first output connection, a second branch of said network including said outdoor temperature responsive impedance and said discharge air temperature responsive impedance and a second output connection, a plurality of branches each including an impedance responsive to the temperature of one of said radiatin means and an impedance responsive to outside wall temperature and each having an output connection, electric amplifier means connected to said first and second output connections and arranged to control said forced air heating apparatus, and additional electric amplifier means arranged to be connected to said first output connection and each of said plurality of output connections for controlling each of said heat radiating means.

2. A temperature control system for a space enclosed by walls, at least one of the walls being exposed to the outside, forced air heating apparatus and a heat radiating means disposed along said outside wall for heating said space, said forced air heating apparatus having an outside air inlet and discharging into said space, space temperature responsive electrical impedance means, electrical impedance means responsive to the temperature of said radiating means, electrical impedance means responsive to a tempera ture indicative of the temperature of the outside surface of said outside wall, impedance means responsive to outside air temperature, impedance means responsive to the temperature of the air discharged into said space, a voltage dividing network circuit having input connections and a plurality of paralle1 branches, the first of said branches including said space temperature responsive means and a first output connection, a second branch of said network including said outdoor temperature responsive impedance and said discharge temperature responsive impedance and a second output connection, and a third branch including the impedance responsive to the outside wall temperature and the impedance responsive to the temperature of said radiating means and having a third output connection,

amplifier means connected to said first and second output connections and arranged to control said forced air heating apparatus, and amplifier means connected to said first output connection and said third output connection for controlling said heat radiating means.

3. A temperature control system for a space enclosed by a plurality of walls including an out= side wall, forced air heating apparatus for heat-= ing said space, electrically controlled means for controlling said apparatus, heat radiating means for heating said space, said heat radiating means being disposed along said outside wall, additional electrically controlled means for controlling heat radiating means, separate follow up potentiometers connected to and operable by each of said electrically controlled means, space temperature responsive electrical impedance means, electrical impedance means responsive to the temperature of said radiating means, electrical impedance means responsive to a condition indicative of outside wall temperature, a voltage dividing network circuit having input connections and a plurality of parallel branches, the first of said branches including said spaced temperature responsive means and a first output connection, a second branch of said network including the follow up potentiometer for the electrical control means for the forced air heating apparatus, the wiper of said potentiometer constituting a second output connection, a third branch including the means responsive to the temperature of said radiating means and the impedance means responsive to the condition indicative of outside wall temperature and additionally including the follow up potentiometer for the electrical means used for controlling said radiating means, the wiper of this potentiometer constituting a third output connection, amplifier means connected to said first and second output connections for controlling said electrically controlled means, and amplifier means connected to said first and third output connections and arranged to control said additional electrically controlled means for the heat radiating means.

4. A temperature control system for a space enclosed by walls wherein a forced air heating apparatus and a heat radiating means is used for heating said space, electrically controlled means for controlling said apparatus, additional electrical means for controlling said heat radiating means, separate follow up means operable by each of said electrical means, space temperature responsive electrical impedance means, impedance means responsive to the temperature of said radiating means, impedance means responsive to a condition indicative of the temperature of one of said Walls, an impedance responsive to outdoor temperature, an impedance responsive to the temperature of the air discharged into said space by said apparatus, a voltage dividing network circuit having a plurality of parallel branches including in a first branch said space temperature responsive means and a first output connection, a second parallel branch including said impedance responsive to the condition indicative of the temperature of said heat radiating means and the impedance responsive to the condition indicative of the side wall temperature and the follow up means for the additional electrical means used for controlling the heat radiating means, the wiper of said follow up means constituting a second output connection, a third parallelbranch including said outdoor temperature responsive impedance and said discharge temperature responsive impedance and the follow up potentiometer for the electrical means used for controlling the forced air heating apparatus, the wiper of this potentiometer being a third output connection, an amplifier-means connected to said first and second output connections and arranged to 13 control the additional electrical means for the heat radiating means, and an amplifier means connected to said first and third output connections for controlling theelectrical means used for controlling said forced air heatin apparatus.

5. A temperature control system for a railway car having an enclosed space heated by a side wall heat exchanger and a forced air'heating apparatus, motor actuated means for controlling the temperature of said side wall heat exchanger, additional motor means for controlling said forced air heating apparatus, an individual follow up potentiometer connected to and operable by each of said motor means, a space temperature responsive means, impedance means responsive to a condition indicative of the temperature or" the side wall heat exchanger, an impedance responsive to a condition indicative of the side Wall temperature of the car, an impedance responsive to outdoor temperature, an impedance responsive to the temperature of the air discharged into said space by said forced air apparatus, a voltage dividing network circuit having input connections and a plurality of parallel branches, the first of said branches including said space temperature responsive means and a first or common output connection, a second parallel branch including said side wall heat exchanger condition responsive means and said side Wall condition responsive means and the follow up potentiometer of the motor means used for controlling said side wall heat exchanger, the wiper of said follow up means constituting a second output connection, a third parallel branch including said outside air temperature responsive impedance and the disi 'ge te 'iperature responsive impedance and up potentiometer for the incr mea s he forced air he. 9-

r of this follow up potentiometer 1 output connection, amplifier I c said first and second output connections and arranged to control the motor actuated means for the side wall heat exchanger, and another amplifier connected to said first and third output connections and arranged to control the motor actuated means for said forced air heating apparatus.

6. A temperature control system for a railway car having an enclosed space heated by a plurality of side wall heat exchangers and a forced air heating apparatus, individual motor actuated means for controlling the temperature of said side wall heat exchangers, additional motor means for controlling said forced air heating means, follow up potentiometer means actuated by each of said motor means, each of said follow up potentiometer means including a resistor and a wiper, a space temperature responsive means, impedance means responsive to the temperature of each of said side wall heat exchangers, impedance means responsive to the temperatures of the outer surfaces of a plurality of the side walls of the car, a network electrical circuit having input connections and a plurality of parallel branches, the first of said branches including said space temperature responsive means and a first output connection, a second parallel branch including the follow up potentiometer of the motor means for controlling said forced air means, the wiper of said potentiometer constituting a second output connection, a third parallel branch including a side wall heat exchanger temperature responsive means and a side wall temperature responsive means and the resistor of the potentiometer actuated by the motor used for control- 14 ling one of saidside wall heat exchangers, the Wiper-of said potentiometer constituting a third output connection afourth branch ofsaid network circuit including another of saidside Wall heat exchanger temperature responsive means and another of said Wall temperature responsive means and the resistor of the followup potentiometer actuated by the motor means for controlling said side wall heat exchanger, the Wiper of this latter potentiometer being used fora fourth output connection, amplifier means connected to said first and second output connections for controlling the additional;motor means for said forced air heating apparatus, and amplifier means connected to said first, third and fourth output connections and individually controlling the motor means which control the side wall exchangers.

'7. Temperature control apparatus for a railway car having overhead heating apparatus and fioor heat radiating means, first actuator means for controlling said overhead apparatus, second actuator means for controlling said fioor heating means, first means responsive to a condition indicative of car temperature, second means responsive to a condition indicative of outside temperature, third means responsive to a condition indicative of the temperature of said fioor heat means, and a balanceable network circuit means having a plurality of parallel branches connecting said first temperature responsive means in control of said first actuator means and for connecting said second and third temperature responsive means in controlling relation to said second actuator means for independent control thereof, said first temperature responsive means being in a difierent branch than said second and third temperature responsive means, said first temperature responsive means being arranged to alter the balance conditions of the entire network circuit.

8. An electrical network circuit having a plurality of voltage dividing parallel branches, a first branch of said network having an output connection common to the network and including a condition responsive impedance means arranged so that variations in its impedance value will affect the balance of the entire network, a second one of said parallel branches including a second output connection and having a plurality of condition responsive impedances so arranged that changes in the impedance sum of said plurality of impedances will cause a signal to appear at said second output connection and a third one of said parallel branches having a third output connection and also having a plurality of condition responsive impedances arranged so that changes in the impedance sum of said impedances in the third branch will cause a signal to appear at said third output connection, the signals appearing at said second and third output connections being normally compared with said common output connection but having a negligible efiect on each other.

9. An electrical network circuit comprising a plurality of parallel branches, the first of said branches having a common output connection and a condition responsive impedance on one side of said output connection, a second parallel branch having a second output connection and a plurality of condition responsive impedances in series, said plurality of impedances being arranged on one side of said second output connection, a third parallel branch having a plu- 15 rality of condition responsive impedance means and a third output connection, said last named plurality of impedances being arranged on one side of said third output connection, and input connections for said network connected to each of said parallel branches, said network being so arranged that a variation in the impedance of the connection responsive means in the first branch causes an output signal to appear across said common output connection and the other output connections and a variation in the impedance of the condition responsive impedances of the second or third branch is capable of causing an output signal across the output connection of the respective branch and the common output 15 connection but has a negligible efiect on the remaining output connection.

CHARLES M. SANDERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date 2,282,442 Whitlock May 12, 1942 FOREIGN PATENTS Number Country Date 540,087 Great Britain Oct. 6, 1941 

